The invention relates to a refining surface of a refiner stator for a refiner intended for defibrating lignocellulose-containing material, the refining surface comprising a feed edge oriented in the direction of the feed flow of the material to be refined, and a discharge edge oriented in the direction of the discharge flow of the material refined, and the refining surface comprising blade bars and blade grooves therebetween, and at least one dam arranged in at least one blade groove, the dam comprising at least one guiding surface, which rises upward from the direction of a bottom of the blade groove, for guiding the material to be refined and the material already refined out of the blade groove.
The invention further relates to a blade segment for a refining surface of a refiner stator for a refiner intended for defibrating lignocellulose-containing material, the blade segment being configurable to constitute part of the entire refining surface of the refiner stator and the blade segment comprising a refining surface comprising a feed edge oriented in the direction of the feed flow of the material to be refined, and a discharge edge oriented in the direction of the discharge flow of the material refined, and the refining surface comprising blade bars and blade grooves therebetween, and a dam arranged in at least one blade groove, the dam comprising at least one guiding surface, which rises upward from the direction of a bottom of the blade groove, for guiding the material to be refined and the material already refined out of the blade groove.
The invention further relates to a refiner for defibrating lignocellulose-containing material, the refiner comprising at least one stator and at least one rotor.
Refiners for making mechanical pulp typically comprise two or more oppositely situated refiner elements that rotate with respect to each other. A fixed, i.e. stationary, refiner element is called a refiner stator and a rotating or rotatable refiner element is called a refiner rotor. In disc refiners, the refiner elements are disc-like and in cone refiners, the refiner elements are conical. In addition to disc refiners and cone refiners, also so-called disc-cone refiners exist, wherein disc-like refiner elements are first arranged in the flow direction of the material to be defibrated, followed by additional refining of the material to be defibrated between the conical refiner elements. Furthermore, cylinder refiners also exist, wherein both the refiner stator and the rotor are cylindrical refiner elements. The refining surfaces of refiner elements are composed of blade bars, i.e. bars, and blade grooves, i.e. grooves, therebetween. The blade bars serve to defibrate the lignocellulose-like material, and the blade grooves serve to convey both the material to be defibrated and that already defibrated on the refining surface. In disc refiners, which are the commonest refiner type, the material to be refined is usually fed to the middle of the stator, i.e. through an opening on the inner circumference of the refining surface of the stator, in between the refining surfaces of the refiner discs, i.e. into a blade gap. The material refined is discharged from the blade gap from the outer circumference of the refining surfaces of the refiner discs to be fed forward in the pulp production process. The refining surfaces of the refiner discs may be either directly formed in the refiner discs or they may be composed of separate blade segments placed adjacent with respect to each other in such a manner that each blade segment constitutes part of the integral refining surface.
Usually, dams connecting two adjacent blade bars are situated in places on the bottom of the blade grooves of the refining surfaces of both the refiner stator and the rotor. The dams serve to guide the material to be refined and the material already refined in between the blade bars of opposite refining surfaces for further refining. The dams include at least one guiding surface that rises upward from the direction of the bottom of the blade groove and whose upward direction is from the direction of the feed edge of the refining surface, i.e. from the edge of the refining surface oriented in the direction of the feed flow of the material to be refined in the direction of the discharge edge of the refining surface, i.e. in the direction of the edge of the refining surface oriented in the direction of the discharge flow of the material refined. Said guiding surface lifts both material to be refined and material already refined out of the blade groove in between opposite refining surfaces. Viewed from the direction of the discharge edges of the refining surfaces, the guiding surfaces of the dams usually end in a vertical surface in such a manner that the material refined and passed the dam can no longer flow backward towards the feed direction of the material to be refined.
Since the dams guide the material to be refined in between opposite blade bars, the dams allow the refining of the material to be enhanced. However, at the same time the dams prevent the passage of the material to be refined on the refining surface by restricting the cross-sectional area of the flow of the blade grooves. This, in turn, generates blockages on the refining surface, which again cause a decrease in the production capacity of the refiner and non-uniformity of the quality of the material refined. This problem is associated particularly with the refining surfaces of refiner stators, since the stationary blade bars of the refining surface of a stationary refiner stator do not exert any special force effect on the material to be refined, which would enhance the passage of the material to be refined in the blade grooves of the refining surface of the refiner stator.